Terminal apparatus

ABSTRACT

A terminal apparatus is provided with a content list storage section that stores a content list storing at least one pair of an address of content related to a position and the position. A position detecting section detects a position, a specifying section which defines a region including an area forward in the traveling direction based on the detected position, and specifies a position in the defined region among positions stored in the content list. A content acquiring section that acquires content corresponding to an address associated with the specified position.

TECHNICAL FIELD

[0001] The present invention relates to a terminal apparatus which ismounted on a mobile unit and used to present content related to aposition.

BACKGROUND ART

[0002] In recent years, with improvement of wireless communicationnetworks including mobile telephone networks, service has becomewidespread that provides content to a terminal apparatus which ismounted and used on a mobile unit such as a car. It is preferable thatthe content to provide to the terminal apparatus mounted on a mobileunit is content related to positions through which the mobile unitpasses.

[0003] For example, a technique called “LOCATIONWARE” is known, as aconventional technique to present to a terminal apparatus the contentrelated to a position which a mobile unit passes through. “LOCATIONWARE”is described in Documents 1 and 2 as described below.

[0004] Document 1: Sakata, et al. “A Proposed “Location-awareNotification Service” Information Processing Society Japan, SIGTechnical Reports on Mobile Computing and Wireless Communication,2000-MBL-15-10, Vol.2000, No.112, pages 78-80, December, 2000.

[0005] Document 2: Kurashima, et al. “Technologies for NotificationService in Location-aware Service Platform “LOCATIONWARE”, NEC TechnicalReport, Vol.54, No.7, 2001.

[0006] In the technique, a server receives a current position andmaximum cache amount of a terminal apparatus from the terminalapparatus. The server sets an acquisition range (cache range) in thevicinity of the received position of the terminal apparatus, andretrieves information (content) related to a position in the acquisitionrange from a position-related information database. The acquisitionrange is set so that the total amount of content data in the acquisitionrange is within the maximum cache amount.

[0007] The server transmits the retrieved content data and informationof the acquisition range to the terminal apparatus. Thus, the contentrelated to the current position is presented to a user of the terminalapparatus.

[0008] Communications between a server and terminal in the conventionaltechnique will be described below with reference to FIG. 1. FIG. 1illustrates communications between the server and terminal apparatus inthe conventional technique.

[0009] In time period B1, terminal apparatus 1702 transmits positioninformation of terminal apparatus 1702 to server 1701. Next, in timeperiod B2, server 1701 calculates an acquisition range based on thereceived position information, and retrieves content data associatedwith the calculated acquisition range. In time period B3, server 1701transmits information of the acquisition range to terminal apparatus1702. In time period B4, server 1701 transmits the content data toterminal apparatus 1702.

[0010] It is necessary to present content related to a position atsuitable timing to a terminal apparatus mounted on a mobile unit whoseposition moves with the passage of time.

[0011] When content related to a position is presented after a mobileunit has passed through the position, the presented content does notrelated to a position of the terminal apparatus, and has little value.

[0012] Further, when loads on the server are large due to concentratedaccess on the server, it takes a time for the server to retrieve contentdata. Therefore, in the conventional technique as disclosed in theabove-mentioned documents, it happens that the mobile unit has movedduring a period of time the server retrieves the content data, and thecontent is not presented to the terminal apparatus at appropriatetiming.

[0013] Timing relating to communications between server 1701 andterminal apparatus 1702 will be described below specifically withreference to FIG. 2. FIG. 2 shows timing relating to communicationsbetween server 1701 and terminal apparatus 1702 in the conventionaltechnique.

[0014] Time axis 1710 shows timing relating to communications betweenserver 1701 and terminal apparatus 1702 in the case where access is notconcentrated on the server.

[0015] In this case, terminal apparatus 1702 starts transmission (B1) ofposition information to server 1701 at time t=0, and server 1701completes transmission (B4) of content data to terminal apparatus 1702before time 1705.

[0016] Time 1705 is the time desired to display the content data toterminal apparatus 1702, and for example, the time the mobile unitmounted with the terminal apparatus passes through the position inrelation to the content data.

[0017] In the timing indicated on time axis 1710, it is possible todisplay the content data to terminal apparatus 1702 appropriately.

[0018] Time axis 1711 shows timing relating to communications betweenserver 1701 and terminal apparatus 1702 in the case were access isconcentrated on the server.

[0019] In this case, terminal apparatus 1702 starts transmission (B1) ofposition information to server 1701 at time t=0, and server 1701completes transmission (B4) of content data to terminal apparatus 1702after time 1705.

[0020] In the timing indicated on time axis 1711, transmission ofcontent data to terminal apparatus 1702 is not completed at time 1705.Therefore, it is not possible to present the content data to terminalapparatus 1702 at appropriate timing.

[0021] This is because concentrated access on server 1701 increases timerequired for server 1701 to calculate an acquisition range and retrievecontend data by time 1704.

[0022] In particular, when a mobile unit mounted with a terminalapparatus moves at high speed, a possibility is high that content datais not presented at appropriate timing due to the fact that the timeincreases required for server 1701 to calculate an acquisition range andretrieve the contend data.

DISCLOSURE OF INVENTION

[0023] It is an object of the present invention to provide a terminalapparatus capable of reducing loads on a server from which the apparatusacquires content data.

[0024] In the present invention, the terminal apparatus stores a contentlist storing at least one pair of an address of content related to aposition and the position, detects a current position, defines a regionincluding an area forward in the traveling direction based on thedetected position, specifies a position in the defined region amongpositions stored in the content list, and acquires content associatedwith the specified position using an address associated with thespecified position.

[0025] By this means, the server from which the content data is acquireddoes not need to perform content retrieval based on the position.Accordingly, it is possible to reduce loads on the server from whichcontent data is acquired.

BRIEF DESCRIPTION OF DRAWINGS

[0026]FIG. 1 is a view illustrating communications between a server anda terminal apparatus in the conventional technique;

[0027]FIG. 2 is a view illustrating timing relating to communicationsbetween the server and the terminal apparatus in the conventionaltechnique;

[0028]FIG. 3 is a view schematically showing a mode where a terminalapparatus is used according to the present invention;

[0029]FIG. 4 is a view illustrating communications between a contentserver and a terminal apparatus of the present invention;

[0030]FIG. 5 is a view illustrating timing relating to communicationsbetween the content server and the terminal apparatus of the presentinvention;

[0031]FIG. 6 is a block diagram illustrating a configuration of acontent distribution system including a terminal apparatus according oneembodiment of the present invention;

[0032]FIG. 7 is a chart showing an example of a data structure of acontent list according to the above embodiment;

[0033]FIG. 8 is a chart showing another example of the data structure ofthe content list according to the above embodiment;

[0034]FIG. 9 is a chart showing still another example of the datastructure of the content list according to the above embodiment;

[0035]FIG. 10 shows the content list represented in XML according to theabove embodiment;

[0036]FIG. 11 is a flowchart for the terminal apparatus to acquirecontent data according to the above embodiment;

[0037]FIG. 12 is a view showing an example of a content data acquisitionregion according to the above embodiment;

[0038]FIG. 13 is a view showing another example of the content dataacquisition region according to the above embodiment;

[0039]FIG. 14 is a view showing still another example of the contentdata acquisition region according to the above embodiment;

[0040]FIG. 15 is a view showing still another example of the contentdata acquisition region according to the above embodiment;

[0041]FIG. 16 is a view showing an example of a scheme of determining asize and a shape of the content data acquisition region according to theabove embodiment;

[0042]FIG. 17 is a view showing another example of the scheme ofdetermining a size and a shape of the content data acquisition regionaccording to the above embodiment;

[0043]FIG. 18 is a flowchart of timing control for the terminalapparatus to display content data according to the above embodiment;

[0044]FIG. 19 is a view showing content data displayed on a displaydevice according to the above embodiment;

[0045]FIG. 20 is a view showing the terminal apparatus acquiring contentdata to enable display of the data as the mobile unit moves according tothe above embodiment;

[0046]FIG. 21 is a view showing an example of a size of the content dataacquisition region when the mobile unit moves at low speed according tothe above embodiment;

[0047]FIG. 22 is a view showing another example of the size of thecontent data acquisition region when the mobile unit moves at high speedaccording to the above embodiment; and

[0048]FIG. 23 is a block diagram illustrating another configuration ofthe content distribution system according to the above embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

[0049] A mode where a terminal apparatus according to the presentinvention is used will be described first with reference to FIG. 3. FIG.3 is a view schematically showing the mode where the terminal apparatusis used according to the present invention.

[0050] Terminal apparatus 101 is mounted and used on mobile unit 143.Mobile unit 143 is, for example, a car, motorbike, bicycle, etc.

[0051] Mounting terminal apparatus 101 on mobile unit 143 means boththat mobile unit 143 is provided with terminal apparatus 101, and that auser brings portable terminal apparatus 101 in mobile unit 143 to usetherein. When a user moves by walk while carrying terminal apparatus101, the user is regarded as a mobile unit.

[0052] Terminal apparatus 101 is, for example, a car navigation systemwith communication function, PDA (Personal Data Assist), notebookpersonal computer or the like. Further, terminal apparatus 101 may be aportable communication terminal such as a cellular telephone and PHS.Furthermore, terminal apparatus 101 may have the function of broadcastreception terminal such as TV broadcast and radiobroadcast.

[0053] Mobile unit 143 moves along path 144. Path 144 may be plannedbeforehand or not planned. Facilities 145 are present at positions nearpath 144.

[0054]FIG. 3 shows a restaurant and gas station as examples offacilities 145. As a matter of course, facilities 145 are not limited tothe aforementioned examples. Facilities 145 may be shopping facilities,sightseeing Facilities and soon, and are only required to have contentdesired to present to users (for example, a driver and/or passenger ofmobile unit 143).

[0055] Mobile unit 143 moves inside predetermined region 146. Forexample, the region 146 is a nation, Kanto area, Kansai are, prefecture,city, town or village. Further, the region 146 may be a specific areadetermined independently of governmental classification. Furthermore,when path 144 is planned in advance, region 146 may be determined to aregion around path 144.

[0056] Terminal apparatus 101 is connected to wide-area road informationserver 102 by wireless communication path 140. Terminal apparatus 101 isfurther connected to content server 103 by wireless communication path141.

[0057] Wide-area road information server 102 and content server 103 are,for example, server computers with arbitrary configurations.

[0058] Wireless communication paths 140 and 141 are, for example,cellular telephone channel, PHS channel, wireless LAN channel, and DSRC.

[0059] In addition, DSRC stands for Dedicated Short Range Communications(local-area communications), and is a communication system currentlyused in the automatic toll collection system of toll road. DSRC isspecifically described in “ITS Information Shower˜All About DSRCsystem”, DSRC System Laboratory, Create-Crews Co., Ltd.

[0060] It is not indispensable that terminal apparatus 101 is directlyconnected to wide-area road information server 102 via wirelesscommunication path 140. Any network (for example, the Internet) and/orwired communication path may be present between terminal apparatus 101and wide-area road information server 102 in addition to wirelesscommunication path 140. As in connection between terminal apparatus 101and wide-area road information server 102, it is not indispensable thatterminal apparatus 101 is connected to content server 103 via wirelesscommunication path 141.

[0061] Content server 103 transmits content data (not shown in FIG. 3,see FIG. 6) to terminal apparatus 101.

[0062] The content data expresses content related to positions offacilities 145. For example, such content may be advertising informationof facilities 145. Content may be road information or sightseeinginformation that is not related to facilities 145. The content is inrelation to a position (for example, position in which each offacilities 145 is present) inside predetermined region 146.

[0063] Terminal apparatus 101 displays the content data that expressessuch content.

[0064] The principal of the present invention will be described belowwith reference to FIG. 4. FIG. 4 is a view illustrating communicationsbetween content server 103 and terminal apparatus 101 of the presentinvention.

[0065] In time period D1, terminal apparatus 101 calculates anacquisition range (content data acquisition region) of content databased on position information of terminal apparatus 101, and searches acontent list for content data related to a position in the content dataacquisition region.

[0066] Next, in time period D2, terminal apparatus 101 transmits arequest for the searched content data to content server 103.

[0067] In time period D3, content server 103 transmits the content datato terminal apparatus 101.

[0068] Timing relating to communications between content server 103 andterminal apparatus 101 of the present invention will be described belowwith reference to FIG. 5. FIG. 5 is a view illustrating timing relatingto the communications between content server 103 and terminal apparatus101 of the present invention.

[0069] First, at time t=0, terminal apparatus 101 starts calculation ofan acquisition range and search of content data, and the server 103 hascompleted transmission of the content data to terminal apparatus 101before time 1805.

[0070] Time 1805 is the time desired to display the content data.

[0071] Thus, in the present invention, terminal apparatus 101 performscalculation of an acquisition range and search. Accordingly, even whenaccess is concentrated on content server 103, a period of time does notextend during which calculation of an acquisition range and search isperformed. Accordingly, terminal apparatus 101 is capable of displayingthe content data appropriately at time 1805.

[0072] One embodiment of the present invention will be describedspecifically below with reference to FIGS. 6 to 22. In thisspecification, the same reference numerals indicate the same structuralelements, and overlapping descriptions may be omitted.

[0073] A configuration of terminal apparatus 101 according to the aboveembodiment will be described below with reference to FIG. 6. FIG. 6 is adiagram illustrating a configuration of content distribution system 600including terminal apparatus 101.

[0074] Terminal apparatus 101 has prefetch scheduler 104, prefetchsection 105, display control section 109, position detecting section110, communication interface 111, storage managing section 112, displaydevice 114 and storage section 113.

[0075] Communication interface 111 communicates with wide-area roadinformation server 102 via wireless communication path 140, and furthercommunicates with content server 103 via wireless communication path141.

[0076] Position detecting section 110 (detecting section) detects aposition of mobile unit 143 (FIG. 3). Position detecting section 110further detects a moving direction and moving speed of the unit 143,etc.

[0077] Position detecting section 110 is, for example, a GPS (GlobalPositioning System) sensor. Further, position detecting section 110 maybe any input device which presents a screen of a map to a user, anddetects a position designated by the user on the presented screen of themap as a position of mobile unit 143. Position detecting section 110 mayoperate in conjunction with a car navigation system (not shown).

[0078] Prefetch scheduler 104 acquires content list 153 from wide-arearoad information server 102 via communication interface 111.

[0079] Content list 153 is, for example, a table that associates aposition inside region 146 (see FIG. 1) with an address of content data152 that expresses content related to the position.

[0080] Specific examples of content list 153 will be described laterwith reference to FIGS. 7 to 9.

[0081] Prefetch section 105 acquires contend data 152 that expresses thecontent from content server 103 via communication interface 111.

[0082] Based on content list 153, prefetch scheduler 104 controls thetiming at which prefetch section 105 acquires content data 152.

[0083] Storage section 113 stores content data 152 acquired from contentserver 103. Storage section 113 is, for example, a hard disk, or may beany memory.

[0084] Storage managing section 112 manages content data 152 stored instorage section 113.

[0085] Display device 114 displays content data 152 stored in storagesection 113. Based on content list 153, display control section 109controls timing at which display device 114 displays content data 152.

[0086] Used as display device 114 is any type of display devicecorresponding to the type of content data 152. When content data 152expresses video, any type of video display device is used as displaydevice 114. When content data 152 expresses audio, any type of audioreplay device is used as display device 114.

[0087] In addition, any type of presentation device may be used, insteadof display device 114. The presentation device includes a printer, etc.

[0088] Content list 153 will be described below with reference to FIG.7. FIG. 7 is a chart showing an example of a data structure of contentlist 153.

[0089] Content list 153 is stored in storage section 113 (FIG. 6) , andreceives access from prefetch scheduler 104 and display control section109. Thus, storage section 113 has the function as a content liststorage section that associates a position in region 146 in relation tocontent with an address of content data 152 expressing the contentrelated to the position to store.

[0090] Content list 153 has record #1 and record #2. Each recordcorresponds to a single item of content data. Each record includes“address” field 201, “position” field 202 and “size” field 203.

[0091] “Address” field 201 stores an address of content data 152. Theaddress of content data 152 indicates, for example, a storage locationof the content in content server 103 (FIG. 6).

[0092] Further, when a network such as the Internet exists betweenterminal apparatus 101 and content server 103, an address of contentdata 152 is an address for uniquely specifying a storage location ofcontent data 152 on the network, for example, a URL address. In thiscase, the address is information for specifying content server 103 onthe network. The URL address is information indicated by “protocolname+host name+directory name+file name”. The host name is a nameassigned to content server 103.

[0093] In the example as shown in FIG. 7, the host name of the contentdata corresponding to record #1 is “www.sample1.com”, and the host nameof the content data corresponding to record #2 is “www.sample2.org”.This means that different servers store the content data correspondingto record #1 and the content data corresponding to record #2.

[0094] Thus, in the present invention, since terminal apparatus 101performs search of content data, different items of content data may bestored in different content servers. It is thereby possible to avoidconcentration of access on a single content server, and to furtherreduce loads on the signal content server.

[0095] In the example as shown in FIG. 7, an address of a top page ofcontent data 152 is described in “address” field 201.

[0096] When content data 152 includes part of images or the like,prefetch scheduler 104 (FIG. 6) that has acquired content list 153obtains an address of the part by analyzing the top page.

[0097] “Position” field 202 stores a position inside region 146 (FIG. 3)to which is related the content expressed by content data 152. In theexample as shown in FIG. 7, the position inside region 146 isrepresented by the latitude and longitude.

[0098] In addition, a mode for representing a position inside region 146is not limited to the foregoing.

[0099] Hereinafter, a position inside region 146 to which content isrelated (i.e. a position inside region 146 to which is related contentdata expressing the content) is referred to as a “content position” inthis specification.

[0100] “Size” field 203 stores a size of content data 152. In theexample as shown in FIG. 7, “size” field 203 stores the size of the toppage.

[0101] Thus, content list 153 is a table that associates at least oneposition (field 202) inside region 146 (FIG. 3) with an address (field201) of each content data related to the at least one position todefine.

[0102] Content list 153 is stored in storage section 113 (FIG. 6). Inother words, storage section 113 functions as a table storage sectionfor storing content list 153 (table).

[0103] In addition, it is not indispensable that content list 153 has“size” field 203.

[0104] Content list 153 is not limited to the example in FIG. 7. Anotherexample of content list 153 will be Described below with reference toFIG. 8. FIG. 8 is a chart showing another example of the data structureof content list 153.

[0105] Content list 153 as shown in FIG. 8 is different from contentlist 153 as shown in FIG. 7 in a value stored in “size” field 203.

[0106] In the example of content list 153 as shown in FIG. 8, “size”field 203 stores the total size of the size of the top page and the sizeof all parts contained in content data 152.

[0107] In this case, only by referring to content list 153, prefetchscheduler 104 is capable of estimating the time required for acquiringcontent data 152.

[0108] Still another example of the data structure of content list 153will be described below with reference to FIG. 9.

[0109] In the example of content list as shown in FIG. 9, respectiveaddresses and sizes of parts contained in content data 152 are describedin content list 153. Specifically, in records #1-1, #1-2, #2-1 and #2-2are described respective addresses and sizes of the parts.

[0110] In this case, only by referring to content list 153, prefetchscheduler 104 is capable of obtaining the respective addresses and sizesof parts contained in content data 152.

[0111] Content list 153 described with reference to FIGS. 7 to 9 arerepresented in any given format. Content list 153 is described, forexample, in XML (extensible Markup Language). XML is a language of whichspecifications are determined by World Wide Web Consortium. World WideWeb Consortium is described in a web page of “http://www.w3.org”.

[0112] An example of representing content list 153 as shown in FIG. 7 inXML will be described below with reference to FIG. 10.

[0113] As shown in FIG. 10, an address of content data 152 is describedin a portion (line 1581) between tag <url> and tag </url> of contentlist 153. A position inside region 146 (FIG. 3) in relation to contentexpressed by content data 152 is described in a portion (line 1582)between tag <location> and tag </location> of content list 153. A sizeof content data 152 is described in a portion (line 1583) between tag<size> and tag </size> of content list 153. Information indicative of anitem of content is described in a portion (content #1) between tag<content> and tag </content> of content list 153. Content #1 correspondsto record #1 (FIG. 7), while content #2 corresponds to record #2 (FIG.7).

[0114] Content data 152 is not limited in representation to XML. Contentdata 152 maybe represented in HTML (Hyper Text Markup Language). HTML isalso a language whose specifications are determined by World Wide WebConsortium.

[0115] Processing for prefetch scheduler 104 to acquire content data 152will be described below with reference to FIG. 11. FIG. 11 is aflowchart illustrating control of the timing for terminal apparatus 101to acquire content data 152.

[0116] The processing as illustrated in FIG. 11 is repeated atpredetermined time intervals always during a period of time mobile unit143 is moving. Further, the processing as illustrated in FIG. 11 may berepeated whenever mobile unit 143 moves a predetermined distance.

[0117] First, prefetch scheduler 104 acquires content list 153 fromwide-area road information server 102 (step S301)

[0118] Prefetch scheduler 104 may acquire content list 153 on broadcastor on demand.

[0119] In the case where prefetch scheduler 104 acquires content list153 on broadcast, wide-area road information server 102 (FIG. 6)broadcasts content list 153 so as to cover region 146 (FIG. 3). Prefetchscheduler 104 receives the broadcast and thereby acquires content list153. The broadcast may be data broadcast such as digital broadcast, forexample.

[0120] In the case where prefetch scheduler 104 acquires content list153 on demand, for example, at the time mobile unit 143 (FIG. 3) entersregion 146, prefetch scheduler 104 transmits a request for content list153 to wide-area road information server 102. Wide-area road informationserver 102 transmits content list 153 to terminal apparatus 101 inresponse to the request from prefetch scheduler 104, and prefetchscheduler 104 receives communications and thereby acquires content list153.

[0121] Prefetch scheduler 104 may acquire content list 153 by readingthe list from an arbitrary storage medium (for example, flexible disk).In this case, wide-area road information server 102 (FIG. 3) is notneeded.

[0122] Thus, prefetch scheduler 104 functions as a table acquiringsection that acquires content list 153 (table) in step 301.

[0123] Step S301 is only required to be performed once at the timemobile unit 143 (FIG. 3) mounted with terminal apparatus 101 entersregion 146 (FIG. 3) (or before the unit 143 enters region 146).

[0124] Content list 153 acquired in step S301 by prefetch scheduler 104is stored in storage section 113. Storage managing section 112 anddisplay control section 109 access stored content list 153.

[0125] Next, position detecting section 110 detects a position of mobileunit 143 (step S302).

[0126] Prefetch scheduler 104 determines a passage expected road basedon the position of mobile unit 143 detected in step S302 (step S303).

[0127] The passage expected road is a road predicted for mobile unit 143to be going to pass. Prefetch scheduler 104 determines the passageexpected road by referring to a road map. Prefetch scheduler 104 mayacquire a road map from wide-area road information server 102 togetherwith content list 153, or may read road map data stored in a storagemedium to acquire.

[0128] In addition, when path 144 (FIG. 3) of mobile unit 143 is alreadyplanned, prefetch scheduler 104 may determine path 144 as a passageexpected road.

[0129] Prefetch scheduler 104 determines a content data acquisitionregion (step S304).

[0130] The content data acquisition region is determined based on theposition of mobile unit 143 detected in position detecting section 110in step S302. Further, prefetch scheduler 104 may determine the contentdata acquisition region in consideration of the passage expected roaddetermined in step S303.

[0131] In addition, examples of the content data acquisition region willbe described later with reference to FIGS. 12 to 15.

[0132] Next, prefetch scheduler 104 notes an item of content data 152(one record) among content list 153 (step S305).

[0133] Prefetch scheduler 104 determines whether the position (contentposition) to which is related the content data 152 noted in step S305 isincluded in the content data acquisition region (step S306).

[0134] When a result of the determination in step S306 is “Yes”,prefetch scheduler 104 proceeds to processing of S307. Meanwhile, when aresult of the determination in step S306 is “No”, prefetch scheduler 104proceeds to processing of step S308.

[0135] In step 307, prefetch scheduler 104 designates the noted contentdata 152 as a candidate for content data to acquire.

[0136] In step S308, prefetch scheduler 104 determines whether or notthe processing of steps S305 to S307 is finished on all the content dataof content list 153.

[0137] When a result of the determination in step S308 is “Yes”,prefetch scheduler 104 proceeds to processing of step S309. Meanwhile,when a result of the determination in step S308 is “No”, prefetchscheduler 104 returns to the processing of step S305.

[0138] In this way, prefetch scheduler 104 executes the processing ofsteps S305 to S307 on each record (content data) included in contentlist 153, and thus, specifies a candidate for content data to acquirefrom items of content data included in content list 153.

[0139] Prefetch scheduler 104 determines non-stored content data amongcandidates for content data to acquire (step S309).

[0140] Non-stored content data is content data that is not stored instorage section 113. Prefetch scheduler 104 determines non-storedcontent data by inquiring whether or not the content data is stored instorage section 113 at storage managing section 112.

[0141] Next, terminal apparatus 101 acquires the non-stored content datafrom content server 103 (step S310).

[0142] Specifically, in step S310, prefetch scheduler 104 functions asan address readout section that reads out an address associated with acontent position of a candidate for content data to acquire from contentlist 153 to provide to prefetch section 105.

[0143] In addition, prefetch scheduler 104 does not read out an addressassociated with a content position of already acquired content data(that is not non-stored content data) among the candidates for contentdata to acquire, every processing in step S310.

[0144] Prefetch section 105 transmits request 151 (FIG. 6) to requestcontent data (non-stored content data) corresponding to the address readout in prefetch scheduler 104 to content server 103.

[0145] In response to request 151, content server 103 transmits thenon-stored content data (content data 152) to terminal apparatus 101.

[0146] Thus, in step S310, prefetch section 105 functions as a contentdata acquiring section that acquires a candidate for content data toacquire.

[0147] In addition, prefetch section 105 does not acquire alreadyacquired content data (that is not non-stored content data) among thecandidates for content data to acquire, every processing in step S310.

[0148] Further, prefetch scheduler 104 may consider time required toacquire non-stored content data (content data 152) when prefetch section105 acquires the non-stored content data from content server 103 in stepS310. Specifically, prefetch section 105 starts acquisition as late aspossible, as long as the non-stored content data is acquired until thedisplay scheduled time. This is because the risk is reduced as much aspossible of excessively acquiring content data 152 that is not displayedeventually, for example, for the reason that mobile unit 143 abruptlychanges the moving direction.

[0149] Prefetch scheduler 104 determines the display scheduled time, forexample, as the time three minutes before the time expected as thedisplay limit time of content data 152.

[0150] When mobile unit 143 passes through the content position ofcontent data 152, the “display limit time” of content data 152 isdefined as the time of the passage. When mobile unit 143 does not passthrough the content position of content data 152, the “display limittime” of content data 152 is defined as the time at which mobile unit143 comes the closest to the content position of content data 152.

[0151] Further, when mobile unit 143 does not pass through the contentposition of content data 152, the “display limit time” may be defined asthe time at which mobile unit 143 passes through a branching location onpath 144 through which mobile unit 143 should pass to arrive at thecontent position of content data 152.

[0152] Prefetch scheduler 104 obtains the time required for acquiringcontent data 152 by dividing the size of the content data 152 by atransmission rate (nominal transmission rate or actual transmissionrate) of wireless communication path 141 (FIG. 6)

[0153] In addition, a plurality of wireless communication paths 141 maybe provided. In this case, prefetch scheduler 104 judges which of theplurality of wireless communication paths 141 allows communications, andfurther may determine wireless communication path 141 to use byconsidering respective transmission rates, communication charges or thelike of wireless communication paths allowing communications.

[0154] In order to judge whether wireless communication path 141 allowscommunications, prefetch scheduler 104 may detect the strength of radiosignal used on wireless communication path 141, or compare a mapindicative of an available area (for example, service area of a cellulartelephone) of wireless communication path 141 with the current positionof terminal apparatus 101. Prefetch scheduler 104 downloads such a map,for example, from wide-area road information server 106 (FIG. 6).

[0155] Thus, terminal apparatus 101 acquires content data 152 includedin the content data acquisition region.

[0156] Content data acquisition region 501 determined in step S304 asshown in FIG. 11 will be described next with reference to FIG. 12. FIG.12 is a view showing an example of content data acquisition region 501according to the above embodiment.

[0157] In FIG. 12, reference numeral “502” indicates a passage expectedroad determined in step S303 (FIG. 11).

[0158] In the example as shown in FIG. 12, content data acquisitionregion 501 is determined as a region, along passage expected road 502,with a predetermined length L forward of mobile unit 143. The length Lmaybe measured along passage expected road 502, or may be the directdistance between opposite ends of content data acquisition region 501.

[0159] In addition, terminal apparatus 101 is capable of recognizingwhich direction is forward of mobile unit 143 among directions alongpassage expected road 502 by the moving direction of mobile unit 143detected in position detecting section 110.

[0160] Further, when the information that passage expected road 502 is aone-way road is obtained from the road map, terminal apparatus 101 iscapable of recognizing which direction is forward of mobile unit 143from the one-way information.

[0161] Content data acquisition region 501 as shown in FIG. 12 ispreferably adopted in the case where passage expected road 502 has fewbranching points such as an intersection and exit like an expressway orfreeway.

[0162] In addition, content data acquisition region 501 is not limitedto that as shown in FIG. 12. Another example of content data acquisitionregion 501 will be described next with reference to FIG. 13. FIG. 13 isa view showing another example of content data acquisition region 501.

[0163] In the example as shown in FIG. 13, content data acquisitionregion 501 is determined as a circular region with mobile unit 143 asits center.

[0164] Content data acquisition region 501 as shown in FIG. 13 ispreferably adopted in the case where there are a lot of branchinglocations (intersections) like a general road. This is because it is notpossible to predict in a general road a direction in which mobile unit143 moves at branching location 503 (intersection) except the case wherepath 144 (see FIG. 3) of mobile unit 143 is beforehand planed, and it isnecessary to determine all the roads branding at branching location 503as passage expected roads.

[0165] Further, in content data acquisition region 501 as shown in FIG.13, a backward area of mobile unit 143 is also determined as a passageexpected road, in consideration of a possibility of a U-turn of mobileunit 143.

[0166] The radius of content data acquisition region 501 may be variedcorresponding to the moving speed of mobile unit 143. In this case,content data acquisition region 501 is determined based on the movingspeed of mobile unit 143 and the position of mobile unit 143.

[0167] As shown in FIGS. 12 and 13, it is possible to acquire contentdata 152 efficiently by defining a shape of content data acquisitionregion 501 corresponding to conditions of roads in the moving directionof mobile unit 143.

[0168] Other examples of the content data acquisition region will bedescribed below with reference to FIGS. 14 and 15. FIGS. 14 and 15further show other examples of content data acquisition region 501.

[0169] Content data acquisition region 501 as shown in FIG. 14 isdetermined as a circular region with the center positioned forward ofmobile unit 143.

[0170] Content data acquisition region 501 as shown in FIG. 15 isdetermined as an ellipse-shaped region extending in the travelingdirection of mobile unit 143. In other words, content data acquisitionregion 501 is determined based on the traveling direction of mobile unit143 and the moving speed of mobile unit 143.

[0171] By determining content data acquisition regions 501 inconsideration of the traveling direction (moving direction) of mobileunit 143 as shown in FIGS. 14 and 15, it is possible to efficientlyacquire content data having the content position in a position forwardof mobile unit 143.

[0172] As shown in FIGS. 12 to 15, content data acquisition region 501(first region) is defined to include at least an area forward of mobileunit 143, based on the position of mobile unit 143 detected in positiondetecting section 110 (FIG. 6).

[0173] The forward of mobile unit 143 is the moving direction in whichmobile unit 143 moves, but the information of moving direction is notalways necessary in defining content data acquisition region 501. Asshown in FIG. 13, even when there is no information of the movingdirection of mobile unit 143, content data acquisition region 501 isdefined to include an area forward of mobile unit 143.

[0174] Thus, prefetch scheduler 104 (FIG. 6) functions as a specifyingsection that specifies a content position associated with a positionwhich mobile unit 143 approaches as a content position for thecandidates of content data to acquire, among at least one contentposition defined in content list 153. Herein, mobile unit 143approaching some position means that the distance between the positionand mobile unit 143 is decreased with time.

[0175] Further, as described above, the size of content data acquisitionregion 501 may be always constant or varied with the speed of mobileunit 143.

[0176] Furthermore, it is not indispensable that position detectingsection 110 (FIG. 6) detects a moving direction and moving speed of themobile unit.

[0177] When the moving speed of mobile unit 143 is known and the movingdirection of mobile unit 143 is unknown, for example, content dataacquisition region 501 is defined as a circle of a size corresponding tothe moving speed with the position of mobile unit 143 as its center.Further, when the moving speed of mobile unit 143 is unknown and themoving direction of mobile unit 143 is known, for example, content dataacquisition region 501 is defined as an ellipse of a constant size witha major axis along the moving direction. When the moving speed andmoving direction of mobile unit 143 are both unknown, for example,content data acquisition region 501 is defined as a circle of a constantsize with the position of mobile unit 143 as its center.

[0178] A scheme of determining content data acquisition region 501 willbe described below with reference to FIG. 16. FIG. 16 is a view showingan example of the scheme of determining a size and a shape of contentdata acquisition region 501.

[0179] In the example as shown in FIG. 16, content data acquisitionregion 501 is determined as a circular region with the center forward ofmobile unit 143.

[0180] The distance between current position 806 of mobile unit 143 andcenter 804 of the circle is set based on the moving speed of mobile unit143. For example, the distance between current position 806 of mobileunit 143 and center 804 of the circle is set at a large value when themoving speed of mobile unit 143 is high, while being set at a smallvalue when the moving speed of mobile unit 143 is low.

[0181] In this case, position detecting section 110 needs to detectmoving direction 803 and the moving speed of mobile unit 143 in additionto current position 806 of mobile unit 143.

[0182] In addition, the distance between current position 806 of mobileunit 143 and center 804 of the circle may be set at a constant value(for example, zero) irrespective of the moving speed of mobile unit 143.

[0183] Radius 805 of the circle is set based on the moving speed ofmobile unit 143. For example, radius 805 is set at a large value whenthe moving speed of mobile unit 143 is high, while being set at a smallvalue when the moving speed of mobile unit 143 is low.

[0184] Further, radius 805 may be set so that the number of items ofcontent data (candidates for content data to acquire) whose contentpositions are included in content data acquisition region 501 is lessthan a predetermined limitation number.

[0185] Furthermore, radius 805 maybe set so that the total size ofcandidates for content data to acquire is less than a predeterminedlimitation value. For example, the size of a candidate for content datato acquire can be recognized by referring to “size” field 203 of contentlist 153 as shown in FIG. 8, or by inquiring at content server 103.

[0186] When content data acquisition region 501 is determined as shownin FIG. 16, content data whose content position meets the relationshipof “(distance between center 804 of the circle and the contentposition)<(radius 805 of the circle)” is designated as a candidate forcontent data to acquire in step S307 (FIG. 11).

[0187] Another scheme of determining content data acquisition region 501will be described below with reference to FIG. 17. FIG. 17 is a viewshowing an example of the scheme of determining a size and a shape ofcontent data acquisition region 501.

[0188] In the example as shown in FIG. 17, content data acquisitionregion 501 is determined as an ellipse-shaped region.

[0189] Content data acquisition region 501 has current position 806 ofmobile unit 143 as one focus and point 803 forward of mobile unit 143 asthe other focus.

[0190] The distance between current position (focus) 806 of mobile unit143 and focus 813 is set based on the moving speed of mobile unit 143.For example, the distance between focuses 806 and 813 is set at a largevalue when the moving speed of mobile unit 143 is high, while being setat a small value when the moving speed of mobile unit 143 is low.

[0191] In this case, position detecting section 110 needs to detectmoving direction 803 and the moving speed of mobile unit 143 in additionto current position 806 of mobile unit 143.

[0192] The distance between focuses 806 and 813 may be set at a constantvalue, irrespective of the moving speed of mobile unit 143.

[0193] Semimajor axis “a” of the ellipse is set based on the movingspeed of mobile unit 143. For example, major axis “a” is set at a largevalue when the moving speed of mobile unit 143 is high, while being setat a small value when the moving speed of mobile unit 143 is low.

[0194] Further, major axis “a” maybe set so that the number of items ofcontent data (candidates for content data to acquire) whose contentpositions are included in content data acquisition region 501 is lessthan a predetermined limitation number.

[0195] Furthermore, major axis “a” may be set so that the total size ofcandidates for content data to acquire is less than a predeterminedlimitation value. When content data acquisition region 501 is determinedas shown in FIG. 17, content data whose content position meets therelationship of “(distance between focus 806 and the contentposition)+(distance between focus 813 and the content position) <2a” isdesignated as a candidate for content data to acquire in step S307 (FIG.11).

[0196] Thus, content data acquisition region 501 is set for anappropriate size based on the position and moving speed of the mobileunit.

[0197] Referring to FIG. 18, the processing will be described below thatterminal apparatus 101 displays content data 152. FIG. 18 is flowchartof timing control for terminal apparatus 101 to display content data152.

[0198] The processing as illustrated in FIG. 18 is repeated atpredetermined time intervals during a period of time mobile unit 143 ismoving. Further, the processing as illustrated in FIG. 18 may berepeated whenever mobile unit 143 moves a predetermined distance.

[0199] Position detecting section 110 detects a position of mobile unit143 (step S701). In step S701, position detecting section 110 furtherdetects the moving speed and moving direction of mobile unit 143.

[0200] Display control section 109 notes an item of content data 152(record) in content list 153 (step S702) Content list 153 is alreadyacquired in step S301 (FIG. 11) Display control section 109 determineswhether or not the position (content position) to which is related thecontent data 152 noted in step S702 is included in a content datadisplay trigger region (second region) (step S703).

[0201] The content data display trigger region is determined based onthe position of mobile unit 143 detected in step S701. The content datadisplay trigger region is determined as a region of positions to whichmobile unit 143 is expected to move, for example, in three minutes(predetermined time).

[0202] Display control section 109 determines whether or not it ispredicted that mobile unit 143 reaches the content position in threeminutes (predetermined time) after moving from the position detected instep S701, and thereby determines whether or not the content position isincluded in the content data display trigger region.

[0203] When a result of the determination in step S703 is “Yes”, displaycontrol section 109 proceeds to processing of S704. Meanwhile, when aresult of the determination in step S703 is “No”, display controlsection 109 proceeds to processing of step S705.

[0204] In step S704, display control section 109 designates the notedcontent data 152 as a candidate for content data to display.

[0205] In step S705, display control section 109 determines whether ornot the processing of steps S702 to S704 is completed on all the contentdata of content list 153.

[0206] When a result of the determination in step S705 is “Yes”, displaycontrol section 109 proceeds to processing of step S706. Meanwhile, whena result of the determination in step S705 is “No”, display controlsection 109 returns to the processing of step S702.

[0207] In step S706, display control section 109 notes one of candidatesfor content data to display.

[0208] Display control section 109 determines whether or not the notedcontent data 152 is stored in storage section 113 (step S707). Displaycontrol section 109 makes such a determination by inquiring at storagemanaging section 112.

[0209] When a result of the determination in step S707 is “Yes”, displaycontrol section 109 proceeds to processing of step S708. Meanwhile, whena result of the determination in step S707 is “No”, display controlsection 109 proceeds to processing of step S709.

[0210] In step S708, display control section 109 instructs storagemanaging section 112 to readout the noted content data 152 from storagesection 113.

[0211] In response to the instruction, storage managing section 112reads out the noted content data 152 from storage section 113.

[0212] In step S709, terminal apparatus 101 acquires the noted contentdata 152 from content server 103 in prefetch section. Prefetch section105 transmits request 151 (FIG. 6) to content server 103 and therebyacquirers the content data 152.

[0213] Next, display control section 109 instructs storage managingsection 112 to store the content data 152 acquired in step S709 (stepS710).

[0214] In response to the instruction, storage managing section 112stores the content data 152 acquired in step S709 in storage section113.

[0215] Terminal apparatus 101 displays the noted content data 152 ondisplay device 114 (step S711).

[0216] Thus, when such a condition (predetermined condition) is met thatthe content position of content data 152 is present inside content datadisplay trigger region 504 (second region), display control section 109and display device 114 function as a display section 149 that displayscontent data 152.

[0217] Content data 152 displayed on display device 114 (FIG. 6) will bedescribed with reference to FIG. 19.

[0218] In region 1107, content data acquisition region 501 and contentdata display trigger region 504 are superimposed and displayed on a roadmap around mobile unit 143.

[0219] Content data 152 is displayed in region 1108. In the example asshown in FIG. 19, content data 152 is advertising information of arestaurant.

[0220] In FIG. 19, triangles with hatchings shown in region 1107indicate content positions 1104 of content included in content datadisplay trigger region 504. White circles indicate content positions1105 that are included in content data acquisition region 501 but arenot included in content data display trigger region 504. A star withhatchings indicates content position 1106 of content data 152 currentlydisplayed in region 1108.

[0221] Each of the triangles with hatchings, while circles and star withhatchings is an indicator indicating a position specified in prefetchscheduler 104 (FIG. 6) as the content position of a candidate forcontent data to acquire in steps S305 to S309 (FIG. 11).

[0222] Region 1108 is set to automatically display content data whosecontent positions are included in content data display trigger region504 sequentially, or may display the content data related to contentposition 1104 in response to a user designating the content position1104 displayed in region 1107.

[0223] A summary of content expressed by the content data and/or name ofa facility related to the content may be displayed on the map (oroutside the map) displayed in region 1107, which is achieved by addingsuch a summary and name of the facility to content list 153.

[0224] Content data acquisition region 501 and content data displaytrigger region 504 both move as mobile unit 143 moves.

[0225] As shown in FIG. 19, content data display trigger region 504 atsome point is determined so that the entire region 504 is included incontent data acquisition region 501 at the some point.

[0226] As described above with reference to FIG. 11, prefetch scheduler104 controls the timing for acquiring content data 152 based on whetherthe content position is included in content data acquisition region 501.Further, as described above with reference to FIG. 18, display controlsection 109 controls the timing for displaying content data 152 based onwhether the content position is included in content data display triggerregion 504.

[0227] Accordingly, display control section 109 controls the timing fordisplaying content data 152 so as to display the content data 152 whenmobile unit 143 is relatively close to the content position of the notedcontent data 152. Meanwhile, prefetch scheduler 104 controls the timingfor acquiring content data 152 so as to acquire (prefetch) the contentdata 152 before the data 152 is displayed on display section 114.

[0228] Only when such “prefetch” is not carried out due to any reason(exception case), a result of the determination in step S707 (FIG. 19)is “No”. Such a result is “Yes” in other cases.

[0229] With reference to FIG. 20, a situation will be described belowwhere terminal apparatus 101 acquires content data and enables displayof the data as mobile unit 143 movies. FIG. 20 is a view showingterminal apparatus 101 acquiring content data to enable display of thedata as mobile unit 143 moves.

[0230] In FIG. 20, the horizontal axis indicates a moving distance ofmobile unit 143. It is assumed that mobile unit 143 moves from the leftside to the right side as viewed in FIG. 20.

[0231] It is further assumed that content data A expresses content Arelated to location 1404, and that content data B expresses content Brelated to location 1405. In other words, locations 1404 and 1405 arerespective content positions of content data A and content data B.

[0232] Distance 1407 indicates the distance from the position of mobileunit 143 to the front end of the content data acquisition region alongthe moving direction (i.e. distance L in the example as shown in FIG.12).

[0233] Distance 1406 indicates the distance from the position of mobileunit 143 to the front end of the content data display trigger regionalong the moving direction.

[0234] Control of the timing for prefetch scheduler 104 to acquirecontent data will be described below with reference to FIG. 20.

[0235] At the time mobile unit 143 exists in location 1411, content dataA enters the content data acquisition region. At this point, contentdata A is acquired (prefetch).

[0236] Similarly, at the time mobile unit 143 exists in location 1412,content data B enters the content data acquisition region. At thispoint, content data B is acquired (prefetch).

[0237] Control of the timing for display control section 109 to displaycontent data will be below described with reference to FIG. 20.

[0238] At the time mobile unit 143 exists in location 1413, content datadisplay trigger region 504 starts including the content position ofcontent data A. At this point, content data A is automatically displayedon display device 114 (FIG. 6).

[0239] Similarly, at the time mobile unit 143 exists in location 1414,content data display trigger region 504 starts including the contentposition of content data B. At this point, content data B isautomatically displayed on display device 114 (FIG. 6).

[0240] In this way, it is possible to display content data A and contentdata B both before passing through respective content positions.

[0241] Further, the content data may be displayed in response to arequest from a user (for example, a driver and/or passenger of mobileunit 143) before being automatically displayed (in other words, beforethe content position of the content data is included in the content datadisplay trigger region). Such a request is, for example, carried out bya user touching an indicator indicative of a content position shown by awhite circle in region 1107 (FIG. 19) on display device 114. In thiscase, it is a premise that the content data has been acquired and isallowed to be displayed.

[0242] On the assumption that the time required to acquire content datais constant irrespective of the moving speed of mobile unit 143, whenthe moving speed of mobile unit 143 is increased, the distance isincreased that mobile unit 143 moves during the time required to acquirethe content data. Accordingly, when the moving speed of mobile unit 143is increased, it is preferable to increase distance 1407 to display thecontent data before passing through its content position. In otherwords, when the moving speed of mobile unit 143 is increased, it ispreferable to increase content data acquisition region 501.

[0243]FIG. 21 is a view showing an example of the size of content dataacquisition region 501 when mobile unit 143 moves at low speed. Further,FIG. 22 is a view showing an example of the size of content dataacquisition region 501 when mobile unit 143 moves at high speed.

[0244] As shown in FIGS. 21 and 22, by defining to vary the length ofcontent data acquisition region 501 along the moving direction of mobileunit 143 corresponding to the moving speed of mobile unit 143, it ispossible to display content data assuredly before passing through itscontent position.

[0245] In the aforementioned embodiment, whether or not to acquirecontent data 152 is only determined corresponding to the condition thatthe content position of content data 152 is included in a content dataacquisition region. However, in addition to the condition, it may bepossible to determine whether or not to acquire content data 152corresponding to conditions such as the time, consecutive traveling timeof mobile unit 143, weather, remaining fuel quantity of mobile unit 143,user preferences and genre of content.

[0246] For example, it may be possible to acquire content dataexpressing content of a restaurant (for example, Japanese restaurant)according to user preferences during meal hours without acquiring thecontent data during hours except the meal hours. Such acquisition isimplemented by adding keyword information to content list 153 andcomparing the keyword information with a database of user preferences.

[0247] For example, such comparison is performed after step S306 asshown in FIG. 11. Further, it may be possible to use such a condition indetermining the order for displaying acquired content data.

[0248] Moreover, it may be possible to acquire content data expressingcontent of a rest place such as a service area and gas station when theconsecutive travel time becomes long, or to acquire content dataexpressing content of indoor rest and/or entertainment facilities whenit rains. Further, it may be possible to acquire only content dataexpressing content of currently operated facilities.

[0249] Terminal apparatus 101 makes a determination on whether contentdata 152 meets a condition such as the time, consecutive traveling timeof mobile unit 143, weather, remaining fuel quantity of mobile unit 143,user preferences and genre of content. Accordingly, a load for thesearch is not imposed on content server 103, and the response of contentserver 103 is improved. Further, the risk is eliminated that userpreferences leak outside.

[0250] As described above, according to the above-mentioned embodiment,content server 103 (that is a server from which content data isacquired) does not need to perform content search based on a position ofmobile unit 143. Accordingly, it is possible to reduce loads on contentserver 103.

[0251] Further, according to the above-mentioned embodiment, terminalapparatus 101 acquires content data having a position associated withthe content data acquisition region including an area forward of mobileunit 143 in the moving direction. It is thereby possible for terminalapparatus 101 to acquire content data before arriving at the position inrelation to the content data. Accordingly, a user of terminal apparatus101 is capable of checking the content data displayed before passingthrough the position in relation to the content data.

[0252] Furthermore, according to the above-mentioned embodiment, thetiming for displaying content data can be controlled based on whetherthe content position is included in the content data display triggerregion. By this means, when mobile unit 143 moves, thereby exists awayfrom the position in relation to the content data that is beforehandprefetch and acquired, and does not need the acquired content data, itis possible not to display the content data.

[0253] Since the content data display trigger region is smaller than thecontent data acquisition region, it is possible to display content dataafter mobile unit 143 comes relatively close to the content position ofthe noted content data. Accordingly, it is possible to effectivelyprevent the content data that has been acquired but becomes unnecessaryfrom being displayed unnecessarily. Thus, the present invention supportsthe case where prefetch content data becomes unnecessary due to movementof mobile unit 143.

[0254] According to the above-mentioned embodiment, it is possible topresent content data at the time the content data display trigger regionstarts including the position of the acquired content data. It is thuspossible to present the content of the position through which mobileunit 143 is expected to pass before mobile unit 143 passes through sucha position, without considering the time required for acquisition.

[0255] Further, according to the above-mentioned embodiment, it ispossible to define to vary the length of content data acquisition regionalong the moving direction of mobile unit 143 corresponding to themoving speed of mobile unit 143. It is thereby possible to acquirecontent data assuredly before passing through its content position anddisplay the data, even when the speed of a mobile unit is high.

[0256] In addition, a mode may be provided with a dedicated server thatsearches for content in response to a position of the terminal apparatusand performs prefetch processing.

[0257] Another content distribution system according to the embodimentof the present invention will be described below with reference to FIG.23. FIG. 23 is a block diagram illustrating another structure of thecontent distribution system.

[0258] Content distribution system 2300 as another example is providedwith terminal apparatus 2301, content retrieval server 2302, wide-arearoad information server 102 and content server 103.

[0259] Terminal apparatus 2301 is connected to content retrieval server2302 via wireless communication path 142. Content retrieval server 2302is connected to wide-area road information server 102 by wirelesscommunication path 140. Content retrieval server 2302 is furtherconnected to content server 103 by wireless communication path 141.

[0260] Terminal apparatus 2301 is provided with position detectingsection 110. Position detecting section 110 is the same as illustratedin FIG. 6, and specific descriptions thereof are omitted. Positiondetecting section 110 detects a position, moving direction, moving speedor the like of terminal apparatus 2301, and outputs the detectedinformation to position transmitting section 2303.

[0261] Position transmitting section 2303 transmits the position, movingdirection, moving speed or the like detected in position detectingsection 110 to content retrieval server 2302 via wireless communicationpath 142.

[0262] Terminal apparatus 2301 is further provided with contentreceiving section 2304 that receives content transmitted from contentretrieval server 2302 via wireless communication path 142. Contentreceiving section 2304 outputs the received content to display device114. Display device 114 displays the content.

[0263] Content retrieval server 2302 is provided with position receivingsection 2305 that receives the position, moving direction, moving speedor the like transmitted from terminal apparatus 2301.

[0264] Content retrieval server 2302 is further provided with prefetchscheduler 104, prefetch section 105, storage managing section 112 andstorage section 113. Prefetch scheduler 104, prefetch section 105,storage managing section 112 and storage section 113 are the same asrespective sections as illustrated in FIG. 6, and specific descriptionsthereof are omitted.

[0265] Content retrieval server 2302 is further provided with contenttransmission control section 2308. Content transmission control section2308 corresponds to display control section 109 as illustrated in FIG.6. While display control section 109 controls the timing for displayingcontent, content transmission control section 2308 controls the timingfor transmitting content. The processing of content transmission controlsection 2308 is processing in FIG. 18 except step S711, which isreplaced with “transmitting content to terminal apparatus 2301 viacontent transmitting section 2309”.

[0266] According to this configuration, terminal apparatus 2301 iscapable of receiving content in response to information in contentreceiving section 2304, only by transmitting the information of theposition, speed, traveling direction or the like to content retrievalserver 2302 from position transmitting section 2302.

[0267] In this way, it is not necessary to provide terminal apparatus2301 with the function of searching for content corresponding to theinformation such as the position to prefetch. As a result, a generalterminal apparatus is applicable as terminal apparatus 2301.Accordingly, the general terminal apparatus is also capable ofpresenting content data appropriately while moving at high speed.

[0268] In addition, in the example as shown in FIG. 23, wide-area roadinformation server 102 is not necessary always. Content retrieval server2302 may have the content list beforehand in storage section 113.

[0269] When content retrieval server 2302 beforehand stores all thecontent, prefetch scheduler 104 and prefetch section 105 are not needed.

[0270] In addition, it may be possible to prepare a program of theprocessing performed by terminal apparatus 101, terminal apparatus 2301or content retrieval server 2302, and make a general computer executethe program to implement the processing of terminal apparatus 101terminal apparatus 2301 or content retrieval server 2302.

[0271] This application is based on the Japanese Patent ApplicationNo.2001-338782 filed on Nov. 2, 2001, entire content of which isexpressly incorporated by reference herein.

[0272] Industrial Applicability

[0273] As described above, according to the present invention, a serverfrom which content data is acquired does not need to search for contentbased on a position of a terminal apparatus. Accordingly, it is possibleto reduce loads on the server.

1. A terminal apparatus that is mounted and used on a mobile unit andthat acquires content related to a position, comprising: a content liststorage section that stores a content list storing at least one pair ofan address of the content and the position; a position detector thatdetects a position of the mobile unit; a specifying section whichdefines a region including an area forward in a traveling direction ofthe mobile unit based on the detected position of the mobile unit, andspecifies the position in the region among positions stored in thecontent list; a content acquiring section that acquires contentassociated with the specified position using the address associated withthe specified position; and a presenting section that presents theacquired content.
 2. The terminal apparatus according to claim 1,wherein the specifying section varies a length of the region along amoving direction of the mobile unit to define corresponding to movingspeed of the mobile unit.
 3. The terminal apparatus according to claim1, wherein the specifying section defines the region corresponding to acondition of a road forward in a moving direction of the mobile unit. 4.The terminal apparatus according to claim 1, further comprising: acontent list acquiring section that acquires the content list byreceiving communications or broadcast.
 5. The terminal apparatusaccording to claim 1, wherein the presenting section presents a map andan indicator indicative of the position specified in the specifyingsection on the map.
 6. The terminal apparatus according to claim 1,further comprising: a presentation controller that determines whether ornot to present the selected content on the presenting section based onthe position of the mobile unit.
 7. The terminal apparatus according toclaim 1, wherein the presentation controller determines a presentationtrigger region that is a region such that the mobile unit is predictedto arrive at the position of the acquired content after moving for apredetermined time, and presents the acquired content when the positionof the acquired content is in the presentation trigger region.
 8. Theterminal apparatus according to claim 7, wherein the presentationcontroller presents the acquired content at the time the presentationtrigger region starts including the position of the acquired content. 9.A content distribution system comprising: the terminal apparatusaccording to claim 1; a list server that stores the content list; and acontent serer that stores the content, wherein the terminal apparatusacquires the content list from the list server via wirelesscommunications, and further acquires the content from the content servervia wireless communications.
 10. A content distribution systemcomprising: a terminal apparatus mounted and used on a mobile unit,having: a position detector that detects a position of the mobile unit;a position transmitter that transmits the detected position of themobile unit; and a content receiver that receives transmitted content,and a server having: a content list storage section that stores acontent list storing at least one pair of an address of content relatedto a position and the position; a position receiver that receives theposition of the mobile unit transmitted from the terminal apparatus; aspecifying section which defines a region including an area forward in atraveling direction of the mobile unit based on the received position ofthe mobile unit, and specifies the position in the region amongpositions stored in the content list; a content acquiring section thatacquires content associated with the specified position using theaddress associated with the specified position; and a contenttransmitter that transmits the acquired content to the terminalapparatus.
 11. A method of acquiring content related to a position of aterminal apparatus mounted and used on a mobile unit, comprising:storing a content list storing at least one pair of an address of thecontent and the position; detecting a position of the mobile unit;defining a region including an area forward in a traveling direction ofthe mobile unit based on the detected position of the mobile unit;specifying the position in the region among positions stored in thecontent list; and acquiring content associated with the specifiedposition using the address associated with the specified position.
 12. Aprogram for a terminal apparatus mounted and used on a mobile unit toacquire content related to a position, the program having a computerexecute: storing a content list storing at least one pair of an addressof the content and the position; detecting a position of the mobileunit; defining a region including an area forward in a travelingdirection of the mobile unit based on the detected position of themobile unit; specifying the position in the region among positionsstored in the content list; and acquiring content associated with thespecified position using the address associated with the specifiedposition.
 13. The terminal apparatus according to claim 1, wherein thespecifying section varies a size of the region to define correspondingto moving speed of the mobile unit.
 14. The terminal apparatus accordingto claim 1, wherein the content acquiring section considers timerequired for acquiring the content to acquire the content before themobile unit passes through the position of the content.
 15. The terminalapparatus according to claim 14, where the content acquiring sectionobtains the time required for acquiring the content by dividing a sizeof the content by a transmission rate of a communication path for use inacquiring the content.